An unprecedented observation of a supernova, an explosion of a massive star, could be captured at its very beginning by an amateur astronomer, just when the supernova became visible in the sky. These early data and additional observations obtained by a battery of telescopes enabled a team of researchers from several CONICET institutes in Argentina and the Department of Astrophysics-Laboratoire AIM (CEA-CNRS-Paris Diderot) in France to test, for the first time, theoretical predictions on the initial evolution of such stellar explosions. These results are published in the journal Nature on February 22, 2018.